Effect of annealing on the structure and electrochemical properties of La1.8Ti0.2MgNi8.9Al0.1 hydrogen storage alloy

La1.8Ti0.2MgNi8.9Al0.1 alloys have been prepared by magnetic levitation melting followed by annealing treatment. The effects of annealing on the structure and electrochemical properties of the alloys are investigated by XRD, SEM-EDS and electrochemical measurement. For as-cast and annealed La1.8Ti0.2MgNi8.9Al0.1 alloys, La(Ni,Al)(5) and LaMg2Ni9 are the main phases. Annealing not only causes LaNi2 phase to disappear, but also brings higher compositional homogeneity, which contributes to the improvement of cycling stability. At 60% discharge capacity retention, the maximum charge-discharge cycles, 160 cycles (at 900 degrees C), is more than three times the minimum, 51 cycles (as-cast). The positive impact of annealing (at 800 degrees C and 900 degrees C) on the charge transfer rate at the surface and the hydrogen diffusion rate in the bulk enhances the HRD. The optimum annealing temperature is found to be 900 degrees C. (C) 2012 Elsevier B.V. All rights reserved.